20 
METHODS IN PLANT HISTOLOGY 
objects may require an hour. No washing is necessary, but all 
plant tissues contain water; consequently, if material is to be 
imbedded in paraffin, the alcohol used for fixing should be poured 
off and fresh alcohol added before proceeding with the clearing. If 
material is to be mounted in Venetian turpentine, as is likely to be the 
case in small filamentous fungi, the transfer to the stain may be 
made directly from the absolute alcohol to any stain dissolved in an 
alcohol not weaker than 85 per cent. Small forms with no vacuoles 
may be transferred to a weaker alcoholic stain or even to an aqueous 
stain; but neither the fixing nor the rude transfer would be at all 
satisfactory with forms like Zyghema or Saprolegnia. 
Acetic acid is used with alcohols to counteract the tendency to 
shrink. One of the most widely known of the alcohol combinations is 
c) Carnoy’s Fluid.— 
Absolute alcohol. 6 parts 
Chloroform. 3 parts 
Glacial acetic acid. 1 part 
The penetration of the reagent is very rapid. An object like an 
onion root-tip is doubtless killed in less than a minute, and 10 to 15 
minutes is long enough for fixing an object of this size. Wash in 
absolute alcohol, changing frequently, until there is little or no odor 
of acetic acid. For a root-tip, the entire process of fixing and wash¬ 
ing should not require more than an hour. It is better to imbed in 
paraffin at once, but when. this is not convenient the material may 
be washed in abolute alcohol until the odor of acetic acid disappears, 
cleared in xylol and, with a block of paraffin about half the bulk of 
the liquid added, may be left indefinitely. Cyanin and erythrosin, 
fuchsin and iodine green, and similar combinations give particularly 
brilliant staining after this reagent. 
d) Acetic Alcohol.—Farmer and Shove recommend for fixing 
root-tips of Tradescantia virginica a mixture of two parts absolute 
alcohol and one part of glacial acetic acid. The mixture is allowed 
to act for 15 to 20 minutes, after which the acid is washed out with 
absolute .alcohol and the material is imbedded as soon as possible. 
e) Formalin Alcohol.—One of the most satisfactory of the alcohol 
combinations is formalin alcohol. Various proportions are used by 
different workers. Professor Lynds Jones, who first brought this 
combination to my notice, added 2 c.c. of commercial formalin to 
